Agricultural spray applications have long included agents to amplify or accelerate the activity of the pesticidal active ingredient. These agents often include nitrogen based fertilizers such as UAN (Urea Ammonium Nitrate) or AMS (Ammonium Sulphate). Although the mechanism is debated the empirical evidence is strong that there is better uptake of selected active ingredients when nitrogen-based agents are incorporated. There are many different pesticide chemistries that include recommendations for addition of nitrogen-based adjuvants; however the greatest numbers of these are herbicides. Pesticides, which includes fungicides, herbicides, insecticides, algicides, moluscicides, miticides and rodenticides, are well known from the state of the art (here, The Pesticide Manual, 14th edition, BCPC 2006, editor CDS Tomlin, is included as a reference, it provides information about the individual mode of actions of active ingredients).
Glyphosate (sodium 2-[(hydroxy-oxido-phosphoryl)methylamino]acetic acid or N(phosphonomethyl)glycine is a non-selective systemic herbicide. Glyphosate, one of the most widely used herbicides, is effective in killing a wide variety of plants, including grasses, broadleaf, and woody plants. Glyphosate is currently supplied in several formulations, including ammonium salt, isopropyl amine salt, potassium salt, and glyphosate acid. Glufosinate is another non-selective herbicide with a different mode of action than glyphosate because translocation only occurs within leaves. Commonly, it is available as ammonium salt.
Spray solutions comprising “hard water” and glyphosate have been demonstrated to have reduced control of unwanted vegetation. “Hard water” is water with high levels of calcium, magnesium, and/or sodium. Other cations may also contribute to hard water. It has been proposed that “hard water” in a spray tank reduces the effectiveness of glyphosate because the cations form a complex with the glyphosate molecule. Glyphosate acts as a chelator or a sequestering agent and forms complexes in the presence of calcium, iron, and magnesium ions. These complexes are incapable of penetrating the epidermal layers of plant leaves and thus reduce the effectiveness of glyphosate as a control agent in unwanted vegetation or weeds.
Adding agents such as ammonium sulphate, for example, to the spray tank, alleviates the problems associated with hard water, by sequestering the cations, and in turn “protecting” the herbicide to penetrate and translocate to the root system of the unwanted vegetation or weed. In addition to ammonium sulphate, phosphoric acid and citric acid are used to sequester, i.e., complex, hard water ions, including Ca2+ and Mg2+, by associating with the glyphosate molecule, thus preventing the Ca2+ and Mg2+ from doing so.
When ammonium (or other sequestering agent) is complexed with the glyphosate or glufosinate molecule, the molecule functions as intended. Large quantities of ammonium sulphate, i.e., 8.5 lbs to 17 lbs per 100 gallons of water (equivalent to 1 to 2 kg/100 l), are currently recommended to provide the desired effect. Ammonium sulphate is limited to water-based formulations. Adding ammonium sulphate may still be beneficial, even when the water is not hard. Some plants, for example, velvetleaf (abutilon theophrastt) contain high levels of calcium in intracellular spaces, and/or have natural defence mechanisms which may also reduce the effectiveness of glyphosate. The addition of ammonium sulphate in these situations also improves the effectiveness of glyphosate.
Many commercial crops have been genetically modified to tolerate glyphosate herbicide sprays, creating a global demand for glyphosate herbicide formulations. The commercial aqueous glyphosate formulation usually contains a surfactant, in addition to other additives, including humectants, anti-gelling agents and anti-freezing agents. The surfactant functions to increase surface wetting, and may also potentiate the active ingredient. Glycerol, a renewable resource, may be used as a humectant in such agricultural spray applications.
One negative effect of the presence of ammonium sulphate in a water spray solutions is its effect on the cloud point of surfactants due to increased electrolyte levels. This effect prevents the formation of stable liquid formulations of glyphosate with ammonium sulfate and a surfactant. Although ammonium sulphate is available in both dry and liquid (40%) forms, end users prefer liquid versions that offer some other functional additives. There are very few surfactants that can be blended with concentrated liquid ammonium sulphate and form single phase products, although alkyl polyglycoside may be added in amounts up to 20% with 40% ammonium sulphate.
What remains is a need for an effective replacement for ammonium sulphate and for suitable nitrogen based adjuvants in other agricultural applications, in particular to form a stable liquid formulation, preferentially containing glyphosate or glufosinate, optionally containing a surfactant to boost the respective biological efficacy, with a sequestering agent for cations, said sequestering agent enhancing the biological performance of active ingredients, too. It has been the object of the present invention to meet this desire of the market.